U.S. patent application number 11/230714 was filed with the patent office on 2006-03-30 for iron-based mixed powder for powder metallurgy and sintered body.
This patent application is currently assigned to JFE STEEL CORPORATION. Invention is credited to Yukiko Ozaki, Hiroshi Sugihara, Satoshi Uenosono.
Application Number | 20060065072 11/230714 |
Document ID | / |
Family ID | 35539657 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060065072 |
Kind Code |
A1 |
Ozaki; Yukiko ; et
al. |
March 30, 2006 |
Iron-based mixed powder for powder metallurgy and sintered body
Abstract
The invention provides an iron-based mixed powder for powder
metallurgy enabling the iron-based mixed powder to improve the
machinability, without being accompanied by degrading the
mechanical property of a sintered body. In order to obtain the
purpose of the invention, the iron-based mixed powder comprises a
mixture of an iron-based powder, a powder for an alloy, a powder
for machinability improvement, while further adding lubricant. And,
(1) the powder for machinability improvement comprises a manganese
sulfide powder, and at least one selected from the group consisting
of a calcium phosphate powder and a hydroxy apatite powder, or, (2)
the powder for machinability improvement has an average particle
diameter of 1 to 60 micrometers and is at least one selected from
the group consisting of manganese sulfide powder and calcium
fluoride powder.
Inventors: |
Ozaki; Yukiko; (Chiba,
JP) ; Sugihara; Hiroshi; (Chiba, JP) ;
Uenosono; Satoshi; (Chiba, JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN & CHICK, PC
220 Fifth Avenue
16TH Floor
NEW YORK
NY
10001-7708
US
|
Assignee: |
JFE STEEL CORPORATION
Tokyo
JP
|
Family ID: |
35539657 |
Appl. No.: |
11/230714 |
Filed: |
September 20, 2005 |
Current U.S.
Class: |
75/231 ;
75/252 |
Current CPC
Class: |
C22C 33/0228 20130101;
B22F 1/0059 20130101 |
Class at
Publication: |
075/231 ;
075/252 |
International
Class: |
C22C 1/05 20060101
C22C001/05 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2004 |
JP |
2004-279335 |
Claims
1. An iron-based mixed powder for powder metallurgy comprising an
iron-based mixed powder made by mixing an iron-based powder, a
powder for an alloy, a powder for machinability improvement and a
lubricant; wherein the powder for machinability improvement
comprises a manganese sulfide powder, and at least one selected
from the group consisting of a calcium phosphate powder and a
hydroxy apatite powder, and, wherein the powder for machinability
improvement is in an amount of 0.1 to 1.0 mass % based on the total
amounts of the iron-based powder, the powder for an alloy, and the
powder for machinability improvement.
2. The iron-based mixed powder for powder metallurgy according to
claim 1, wherein the powder for machinability improvement comprises
the calcium phosphate powder which is at least one selected from
the group consisting of tricalcium phosphate, calcium hydrogen
phosphate and calcium dihydrogen phosphate.
3. The iron-based mixed powder for powder metallurgy according to
claim 1, wherein the powder for machinability improvement has an
average particle diameter of 0.1 to 20 micrometers.
4. The iron-based mixed powder for powder metallurgy according to
claim 2, wherein the powder for machinability improvement has an
average particle diameter of 0.1 to 20 micrometers.
5. The iron-based mixed powder for powder metallurgy according to
any one of claims 1 to 4, which further comprises at lease one
binder.
6. The iron-based mixed powder for powder metallurgy according to
any one of claims 1 to 4, wherein each of the manganese sulfide
powder and the calcium phosphate powder and/or the hydroxy apatite
powder has an average particle diameter of 0.1 to 20 micrometers;
and the powder for machinability improvement contains the manganese
sulfide powder in an amount of 10 to 80 mass % based on the total
amount of the powder for machinability improvement.
7. The iron-based mixed powder for powder metallurgy according to
claim 1, wherein the iron-based powder is at least one powder
selected from the group consisting of an atomized iron powder a
reduced iron powder, a prealloyed steel powder and a partially
alloyed steel powder; and wherein the powder for an alloy is at
least one powder selected from the group consisting of a graphite
powder, a copper powder, a nickel powder and a molybdenum
powder.
8. An iron-based sintered body made by a process comprising
compacting the iron-based mixed powder for powder metallurgy
according to any one of claims 1 to 4, and subsequently sintering
the resultant compacted iron-based mixed powder.
9. An iron-based mixed powder for powder metallurgy comprising: an
iron-based mixed powder made by mixing an iron-based powder, a
powder for an alloy, a powder for a machinability improvement and a
lubricant; wherein the powder for machinability improvement is at
least one selected from the group consisting of manganese sulfide
powder and calcium fluoride powder; wherein the powder for the
machinability improvement has an average particle diameter of 1 to
60 micrometers; and wherein the powder for machinability
improvement is in an amount of 0.1 to 1.5 mass % based on the total
amounts of the iron-based powder, the powder for an alloy, and the
powder for machinability improvement.
10. The iron-based mixed powder for powder metallurgy according to
claim 9, wherein at least one of the manganese sulfide powder and
the calcium fluoride powder has a particle size distribution that
is substantially the same as the size distribution of pores of a
sintered body obtained by compacting the iron-based mixed powder
without adding the manganese sulfide powder or the calcium fluoride
powder and by sintering the resultant compacted iron-based mixed
powder.
11. The iron-based mixed powder for powder metallurgy according to
claim 9, wherein an average particle diameter of the manganese
sulfide powder is 1 to 10 micrometers and an average particle
diameter of calcium fluoride powder is 20 to 60 micrometers;
wherein the content of the calcium fluoride powder is 20 to 80 mass
% based on the total amounts of the manganese sulfide powder and
the calcium fluoride powder.
12. The iron-based mixed powder for powder metallurgy according to
claim 10, wherein an average particle diameter of the manganese
sulfide powder is 1 to 10 micrometers and an average particle
diameter of calcium fluoride powder is 20 to 60 micrometers;
wherein the content of the calcium fluoride powder is 20 to 80 mass
% based on the total amounts of the manganese sulfide powder and
the calcium fluoride powder.
13. The iron-based mixed powder for powder metallurgy according to
any one of claims 9 to 12, which further comprises at lease one
binder.
14. The iron-based mixed powder for powder metallurgy according to
any one of the claim 9, wherein the iron-based powder is at least
one powder selected from the group consisting of an atomized iron
powder, a reduced iron powder, a prealloyed steel powder and a
partially alloyed steel powder; and wherein the powder for an alloy
is at least one powder selected from the group consisting of a
graphite powder, a copper powder, a nickel powder and a molybdenum
powder.
15. An iron-based sintered body made by a process comprising
compacting the iron-based mixed powder for powder metallurgy
according to claim 13, and subsequently sintering the resultant
compacted iron-based mixed powder.
16. An iron-based sintered body made by a process comprising
compacting the iron-based mixed powder for powder metallurgy
according to claim 12, and subsequently sintering the resultant
compacted iron-based mixed powder.
Description
TECHNICAL FIELD
[0001] This invention relates to the iron-based mixed powder for
powder metallurgy, and relates to the iron-based mixed powder for
powder metallurgy that enables especially the machinability
improvement of a sintered body.
BACKGROUND ART
[0002] Recently, progress of powder metallurgy technology makes it
possible to produce the complicated form in need of high
dimensional accuracy into near-net-form. And the products that are
manufactured by making use of the powder metallurgy technology
becomes applicable to a variety of technological fields.
[0003] The iron-based mixed powder for powder metallurgy is
produced as follows. At first, iron-based mixed powder, which is
produced by mixing a powder for an alloy and a lubricant with
iron-based powder, is filled up in a die cavity. Here, the powder
for an alloy is one such as copper powder or graphite powder. The
lubricant is one such as zinc stearate or lithium stearate. Second,
they are pressurized to be formed, and subsequently they are
subjected to sintering process to become a sintered body. Third, in
accordance with the necessity, they are fabricated by cutting to be
a final product.
[0004] Thus, the sintered body that is manufactured in such a way
has a high porosity. At the moment, the sintered body has a high
cutting-resistance (cutting-force), compared with metal materials
produced by the melting method such as wrought steel and cast iron.
For such a reason, it has conventionally been done to add a various
sorts of powder such as Pb, Se, Te, Mn, S and so forth to
iron-based powder, or to add such elements to the iron-based powder
by alloying in an atomizing process. Such treatment has been done
in order to improve the machinability of a sintered body.
[0005] However, since the melting point of Pb is as low as 330
degrees C., Pb melts in the midway of the sintering process. At the
same moment, since Pb is not soluble into the ferrite, a problem
happens that it is difficult to carry out uniform distribution of
Pb all over a matrix. Moreover, because Se and Te embrittle the
sintered body, a problem happens that degrading the mechanical
property of the sintered body is significant.
[0006] As for adding the powder, in order to improve machinability,
it is proposed that a variety of powders other than the
above-mentioned ones are added.
[0007] As one example, addition of inorganic compound powder of
high hardness to the iron-based mixed powder, as a chipping
promotion material, is proposed. In this method, particles of the
inorganic compound powder become a concentrating points of stress,
when a part to be cut carries out plastic deformation at the time
of cutting, and enforce the cut-scraps to be a small size, thereby
reduce the contact surface area between a cutting tool and scraps
to lower frictional resistance, and thereby prevent tool wear.
[0008] For example, in the Japanese Unexamined Patent Application
Publication No. 61-147801, it is proposed to mix 0.05 to 5 mass %
of manganese sulfide (MnS) powder of 10 micrometers or less in size
into iron powder. Further, the Japanese Examined Patent Publication
No. 46-39654 proposes a method for preparing a chipping promotion
material, which means, adding BaSO.sub.4 or BaS independently or in
combination. And furthermore, in the Japanese Unexamined Patent
Application Publication No. 2002-155301, fluorides of alkaline
earth metals such as CaF.sub.2, MgF.sub.2, SrF, and BaF.sub.2. are
proposed. Similarly, in the Japanese Patent No. 3073526, addition
of the molten mixture of CaF.sub.2 and BaF.sub.2, or the
combination of MnS and molten mixture of CaF.sub.2 and BaF.sub.2 is
proposed.
[0009] Although such addition of chipping promotion material
reduces the contact surface area between a cutting tool and scraps
like the above and it is effective on lowering the frictional
resistance, there is no function, which protects the tool surface,
such as suppressing oxidization caused by frictional heat. (Here,
the frictional heat generates on cutting.) And since an
intermittent impact is further given to a tool at an intermittent
collision between the tool and surfaces forming pores in a sintered
body, there is a problem of quality-of-the-material degradation by
oxidization on the surface of a tool, or a chip or fracture of the
tool by generating the fine sized crack inside the tool by the
intermittence impact.
[0010] As a method of preventing deterioration of the tool surface
under cutting typified by oxidization, it is proposed to distribute
the ceramics of the low melting point beforehand in a work
material, to soften the ceramic particles exposed to the working
side at the time of cutting, by the frictional heat, and to make
the ceramic particles adhere and spread on the tool surface, and to
make a tool protective film, what is called, an overlaying layer
form. For example, Japanese Unexamined Patent Application
Publication No. 9(1997)-279204 proposes such an iron-based mixed
powder for powder metallurgy, which contains
CaO--Al.sub.2O.sub.3--SiO.sub.2 based compound oxide powder of 0.02
to 0.3 mass % as the ceramic powder of low melting point, which has
anorthite-phase and/or gehlenite-phase, and whose average particle
diameter is 50 micrometers or less, in an iron powder as main
ingredient.
[0011] However, there is a problem that in some cutting conditions,
generation of frictional heat between tool and a work material is
insufficient, and the low fusing point ceramics does not become
soft, and therefore tool protective film is not formed.
DISCLOSURE OF INVENTION
[0012] The purpose of this invention is to solve the problem of the
above-mentioned conventional technology advantageously. This
invention aims at offering the iron-based mixed powder for powder
metallurgy, which can improve machinability, without being
accompanied by degrading the mechanical property of a sintered
body.
[0013] In the present invention, `machinability` is defined as, in
another word, `easiness to be cut`, at the time when cutting-work
is done. Such machinability is expressed by the following factors.
That is to say, cutting-resistance, durability of a tool
(tool-life), degree of roughness on the finishing-surface, a figure
of the cutting-scraps and so forth.
[0014] As the first embodiment in order to attain the
above-mentioned subject, the inventors of the present invention did
investigation wholeheartedly, while taking notice on MnS as powder
for machinability improvement, concerning how co-addition of the
additional powder for machinability improvement influences on the
further improvement in machinability. As a result, the inventors
have conceived that as the powder for machinability improvement,
additional to MnS, co-addition of calcium phosphate and/or the
hydroxy apatite remarkably improves machinability without being
accompanied by degradation of mechanical property, compared with
adding MnS independently. Although the exact mechanism of this
improvement in machinability does not appear to be clear at
present, these inventors esteem and conclude as follows.
[0015] As for MnS, it is said that the effect of the machinability
improvement is caused by so-called a chipping effect that makes
cutting-scraps a fine small size. However, the tool surface
contacts a work material (the material to be cut) directly and
generates heat by friction in the atmosphere, the quality of the
material of a tool deteriorates by oxidization on the surface of a
tool. Therefore, such a chipping effect cannot obtain a sufficient
result such as remarkable reduction of tool wear, leading to a
remarkable improvement of machinability.
[0016] When, additional to MnS, calcium phosphate and/or the
hydroxy apatite is co-added, and distributed in a sintered body,
the particles of calcium phosphate and/or hydroxy apatite which are
exposed to the working-side (cut area to be worked) at the time of
cutting adhere on the surface of a tool, resulting in forming a
tool protective film, while MnS promotes cutting-scraps to be a
fine small-sized ones. Resultantly, above mechanisms prevent or
suppress deterioration of the tool surface at the time of cutting,
ending up in improving a tool life notably.
[0017] As the second embodiment, the inventors of the present
invention have found out that addition of manganese sulfide powder
and/or calcium fluoride powder, whose average particle diameter is
1 to 60 micrometers, are effective on attaining such a purpose.
[0018] Based on the above-mentioned knowledge, this invention
proceeds further examination and is evolved to be completed.
[0019] This invention is summarized as follows.
[0020] (1) An iron-based mixed powder for powder metallurgy
comprising an iron-based mixed powder made by mixing an iron-based
powder, a powder for an alloy, and a powder for a machinability
improvement, and a lubricant;
[0021] wherein the powder for machinability improvement comprises a
manganese sulfide powder, and at least one selected from the group
consisting of a calcium phosphate powder and a hydroxy apatite
powder, and,
[0022] wherein the powder for machinability improvement comprises a
manganese sulfide powder, and at least one selected from the group
consisting of a calcium phosphate powder and a hydroxy apatite
powder, and,
[0023] wherein the powder for machinability improvement is in an
amount of 0.1 to 1.0 mass % based on the total amounts of the
iron-based powder, the powder for an alloy, and the powder for
machinability improvement.
[0024] (2) The iron-based mixed powder for powder metallurgy
according to (1), wherein the powder for machinability improvement
comprises the calcium phosphate powder which is at least one
selected from the group consisting of tricalcium phosphate, calcium
hydrogen phosphate, and calcium dihydrogen phosphate.
[0025] (3) The iron-based mixed powder for powder metallurgy
according to (1) or (2), wherein the powder for machinability
improvement has an average particle diameter of 0.1 to 20
micrometers.
[0026] (4) The iron-based mixed powder for powder metallurgy
according to any one of (1) to (3), which further comprises at
lease one binder.
[0027] In this embodiment, it is preferable that a part or all
parts of the iron-based powder has a surface onto which at least
one powder selected from the group consisting of the powder for an
alloy and the powder for machinability improvement adheres by a
binder.
[0028] (5) An iron-based sintered body made by a process comprising
compacting the iron-based mixed powder for powder metallurgy
according to any one of (1) to (4), and subsequently sintering the
resultant compacted iron-based mixed powder.
[0029] (6) An iron-based mixed powder for powder metallurgy
comprising:
[0030] an iron-based mixed powder made by mixing an iron-based
powder, a powder for an alloy, a powder for a machinability
improvement and a lubricant;
[0031] wherein the powder for machinability improvement is at least
one selected from the group consisting of manganese sulfide powder
and calcium fluoride powder; wherein the powder for the
machinability improvement has an average particle diameter of 1 to
60 micrometers; and wherein the powder for machinability
improvement is in an amount of 0.1 to 1.5 mass % based on the total
amounts of the iron-based powder, the powder for an alloy, and the
powder for machinability improvement.
[0032] (7) The iron-based mixed powder for powder metallurgy
according to (6), wherein at least one of the manganese sulfide
powder and the calcium fluoride powder has a particle size
distribution that is substantially the same as the size
distribution of pores of a sintered body obtained by compacting the
iron-based mixed powder without adding the manganese sulfide powder
or the calcium fluoride powder and by sintering the resultant
compacted iron-based mixed powder.
[0033] (8) The iron-based mixed powder for powder metallurgy
according to (6) or (7), wherein an average particle diameter of
the manganese sulfide powder is 1 to 10 micrometers and an average
particle diameter of calcium fluoride powder is 20 to 60
micrometers; wherein the content of the calcium fluoride powder is
20 to 80 mass % based on the total amounts of the manganese sulfide
powder and the calcium fluoride powder.
[0034] (9) The iron-based mixed powder for powder metallurgy
according to any one of (6) to (8), which further comprises at
lease one binder
[0035] In this embodiment, it is preferable that a part or all
parts of the iron-based powder has a surface onto which at least
one powder selected from the group consisting of the powder for an
alloy and the powder for machinability improvement adheres by a
binder.
[0036] (10) An iron-based sintered body made by a process
comprising compacting the iron-based mixed powder for powder
metallurgy according to (8) or (9), and subsequently sintering the
resultant compacted iron-based mixed powder.
BRIEF EXPLANATION OF THE DRAWINGS
[0037] FIG. 1 is a general conceptual drawing of a wear of rake
face, a flank wear of clearance face and a wear depth of clearance
face, when machinability in turning using a byte is evaluated in
the testing method of the present invention.
[0038] FIG. 2 is a conceptual drawing of the present invention,
showing a relative relation of the respective positions about the
specimen (a sintered body as a final product of the iron-based
mixed powder) and a tool (cemented-carbide byte), when
machinability in turning using a byte is evaluated in the testing
method of the present invention.
[0039] FIG. 3 is a conceptual drawing of the present invention,
showing a wear of circumferential relief surface and a maximum
outer flank wear depth of cutting edge, when machinability is
evaluated in the testing method of the present invention, when
using a drill.
[0040] FIG. 4 shows torque and amplitude of the vibration of
torque, on a chart of the torque on the time-passage, when
machinability is evaluated in the testing method of the present
invention, when using a drill.
PREFERABLE EMBODIMENTS
First Embodiment
[0041] An iron-based mixed powder for powder metallurgy of this
invention is an iron-based mixed powder made by mixing an
iron-based powder, a powder for an alloy, a powder for
machinability improvement, and a lubricant.
<Powder for Machinability Improvement>
[0042] In this invention, as a powder for machinability
improvement, a manganese sulfide powder is contained. Even
furthermore, a calcium phosphate powder and/or a hydroxy apatite
powder are contained. In addition, it may be a case, the fluoride
of alkaline-earth metals, such as calcium fluoride, is further
contained.
[0043] The manganese sulfide powder for machinability improvement
provides a concentrating point of stress when a sintered body is
cut off. Therefore, the manganese sulfide powder enforces
cutting-scraps to be a fine small size. And therefore the manganese
sulfide powder reduces the contact surface area of a cutting tool
and cutting-scraps, and further reduces friction-resistance that
occurs on the contact surface, resulting in the function of
improving machinability. As for the content of manganese sulfide,
it is desirable to be fallen within a range of 10 to 80 mass %,
based on the sum total amount of the powder for machinability
improvement. The reason why is that the above-mentioned effect is
not notable, under the condition that the content of the manganese
sulfide is less than 10 mass %, based on the sum total amount of
the powder for machinability improvement. On the other hand, if the
content of manganese sulfide exceeds 80 mass %, the mechanical
property of a sintered body degrades. Further, the amount of the
component for forming tool protective film decreases, and thereby
the tool-surface deteriorates, resulting in enforcing a tool-life
(tool-durability) to fall down.
[0044] Although the particle diameter of the manganese sulfide
powder is preferable to be selected in accordance with the usage,
the average particle diameter size of 0.1 to 20 micrometers is
preferable. Because, within a range of an average particle diameter
of less than 0.1 micrometer, the distribution of stress
concentration point gets to sparse, resulting in degrading the
effect of enforcing fine small sized cutting-scraps. On the
contrary, in case that an average particle diameter becomes large
exceeding 20 micrometers, the compressibility of the iron-based
mixed powder falls down unpreferably. More preferable minimum value
of the average particle diameter is 1 micrometer. More preferable
maximum value of the average particle diameter is 10 micrometers.
Here, a laser diffraction-scattering method measures the particle
diameter of the powder. The respective average diameters are
defined as a value acquired when accumulation percent by mass is
50%.
[0045] In this invention, as the powder for machinability
improvement, additional to MnS, the calcium phosphate powder and/or
hydroxy apatite powder are contained further.
[0046] Calcium phosphate powder and/or hydroxy apatite powder
distribute in a sintered body. And they expose to the working
surface (cutting-surface) of a sintered body at the time of
cutting, and calcium phosphate and a hydroxy apatite adhere to the
tool surface at the time of cutting, and form a tool protective
film. Deterioration of tools, such as oxidization, is prevented or
suppressed by formation of a tool protective film. Resultantly,
tool-durability becomes long, and machinability is improved. In
addition, even in case that the sintered body contains calcium
phosphate and a hydroxy apatite, very few degree of degrading in
the mechanical property of a sintered body is observed, because no
interaction occurs with the iron-based powder at the time of
sintering. Calcium phosphate and a hydroxy apatite may be contained
independently, or in combination. Addition in combination enables
the corresponding effect to become more remarkable, than
independent addition.
[0047] As for the average particle diameter of the additive calcium
phosphate powder and/or additive hydroxy apatite powder, in the
range of 0.1 to 20 micrometers is desirable, and in the range of 1
to 10 micrometers is more preferable. If the average particle
diameter of calcium phosphate powder and/or hydroxy apatite powder
is less than 0.1 micrometer, particles are buried in whole matrix
of a sintered body. In consequence of it, a tool protective film
becomes hard to be formed. On the other hand, in case that the
average particle diameter exceeds 20 micrometers, it is hard to
form a uniform film on the tool surface. Therefore, cutting
temperature rises and oxidization of the tool surface advances.
Furthermore, the softened cutting-scraps adhere to the edge of a
blade. This enforces the roughness of machined surface to be
coarse. It is not desirable.
[0048] As the calcium phosphate used in this embodiment, each of
tricalcium phosphate (Ca.sub.3(PO.sub.4).sub.2), calcium hydrogen
phosphate (CaHPO.sub.4, CaHPO.sub.4.2H.sub.2O), and calcium
dihydrogen phosphate (Ca(H.sub.2PO.sub.4).sub.2,
Ca(H.sub.2PO.sub.4).sub.2.H.sub.2O) can be used preferably. In
addition, from a viewpoint of the stability of a tool protective
film, it is more desirable to use tricalcium phosphate
(Ca.sub.3(PO.sub.4).sub.2) and/or calcium hydrogen phosphate
(CaHPO.sub.4, CaHPO.sub.4.2H.sub.2O).
[0049] A hydroxy apatite (Ca.sub.10(PO.sub.4).sub.6(OH).sub.2) has
the same function as calcium phosphate. A hydroxy apatite can be
used, alone or in combination with calcium phosphate.
[0050] It may be a case that the fluoride of alkaline earth metals
is further, contained, in addition to MnS powder and calcium
phosphate powder and/or hydroxy apatite powder. As fluoride of
alkaline earth metals, calcium fluoride, magnesium fluoride,
fluoridation strontium, barium fluoride, etc. can be illustrated.
As for the content of the fluoride of alkaline-earth metals, it is
desirable to be fallen within the range of the sum total content of
the powder for a machinability improvement, described as
follows.
[0051] In the iron-based mixed powder for powder metallurgy of this
invention, preferably, the powder for a machinability improvement
has a content amount of 0.1 to 1.0 mass % in total based on the
amount of sum totals of the iron-based powder, the powder for an
alloy, and the powder for a machinability improvement. If the
content of the sum total of the powder for a machinability
improvement is less than 0.1 mass %, the remarkable improvement in
machinability is not evident. On the other hand, in case that the
content exceeds 1.0 mass %, degradation in compressibility and
compressive rapture strength becomes unpreferably large. In
contrast, in case that the content of the powder for a
machinability improvement falls within the range of 0.1 to 1.0 mass
%, the rate of a dimensional change of a sintered body also becomes
small, resulting in no problem from a standing point of keeping
accuracy of dimension. For this reason, the content of the powder
for a machinability improvement is, in total, taken as 0.1 to 1.0
mass % based on the amount of sum totals of the iron-based powder,
the powder for an alloy, and the powder for a machinability
improvement. It is preferable to keep the content within 0.3 to 0.5
mass % based on the amount of sum totals of iron-based powder, the
powder for an alloy, and the powder for a machinability
improvement.
[0052] In addition, from a technical viewpoint of homogeneous
characteristic concerning the mixed powder, the maximum particle
diameter of the powder for machinability improvement is preferable
to be 45 micrometers or less. It is 20 micrometers or less more
preferably. Moreover, as for the average particle diameter of
powder for machinability improvement, such as MnS, as described
above, it is preferable to be referred to as 0.1 to 20 micrometers,
or more preferably, 1 to 10 micrometers.
<Iron-Based Powder, Powder for an Alloy, and Lubricant>
[0053] As the iron-based powder, each pure iron powder, such as
atomized iron powder and reduced iron powder, can be used
preferably in this invention. Moreover, the following alloyed steel
powder can be replaced with the iron powder. That is to say, a
prealloyed steel powder that alloyed the alloying element
beforehand, and a partially alloyed steel powder in which the
alloying element powder was attached on the particle of pure iron
powder or prealloyed steel powder beforehand. In addition, it
invites no problem to mix and use the above-mentioned sorts of the
iron-based powders.
[0054] As the powder for an alloy used in this invention, following
ones are exemplified. These are, a graphite powder, various
metallic powders such as copper powder, nickel powder, molybdenum
powder and so forth. It is desirable to select the sorts of the
powders appropriately and to carry out the predetermined quantity
content according to the respective required product
characteristics. From a viewpoint of no deteriorating the
mechanical strength of a sintered body, it is preferable to limit
to the range of 0.1 to 4 mass % based on the amount of the sum
total of the iron-based powder, the powder for an alloy, and the
powder for machinabihty improvement. More preferable content is 2
mass % or less, and further preferable content is 1.0 mass % or
less.
[0055] As lubricant contained in the iron-based mixed powder of
this invention, metal soap such as zinc stearate, lithium stearate
and so forth, or wax or the like is preferable. Although the amount
of the lubricant to be blended is not limited in particular by this
invention, the blending amount of the lubricant is preferable to be
a 0.2 to 1.5 mass part based on the amount of the sum total 100
mass part (Here, the sum total 100 mass part constitutes of
iron-based powder, the powder for an alloy, and machinability
improvement particle powder.). The reason why is; in case that the
blending amount of the lubricant is under in 0.2 mass part,
friction with a die increases, ejection force increases, and die
life falls down. On the other hand, in case that blending amount of
the lubricant exceeds 1.5 mass parts, green density decreases,
resulting in reducing of sintered density.
<Production Method>
[0056] Below, the preferable production method of the iron-based
mixed powder of this invention is explained.
[0057] As a method for producing the iron-based mixed powder, it is
preferable to blend the predetermined amount of the powder for an
alloy, the powder for the machinability improvement, and the
lubricant, into the above-mentioned iron-based powder, and it is
preferable to use usually well-known blenders, such as V shaped
blender or double-cone blender. Mixing can be done at once, or in
two or more steps to be an iron-based mixed powder. In order to
produce the iron-based mixed powder, it may be a case, the
iron-based powder is used, which has already performed
segregation-preventing treatment. In this case, such treatment is
done in such a way that a part or all parts of the powder for an
alloy and/or a part or all parts of the powder for machinability
improvement adheres to the surface of a part or all parts of the
iron-based powder, utilizing a binder. Thereby, the iron-based
mixed powder comes to have much less segregation, simultaneously
with excelling in flowability to a great degree.
[0058] With regard to the segregation-preventing treatment, a
method may be used, which is described in the Japanese Patent No.
3004800. Namely, the powder for an alloy and/or the powder for
machinability improvement are mixed with the iron-based powder,
while adding a particular organic matter that has the function of
gluing powder particles (hereinafter simply named as `binder`).
Subsequently, it is heated up to 10 degrees C. or more, in
comparison with the melting point (minimum value of the melting
points of binder in case that there are two or more sorts of the
binders). Preferably, it is heated up to 15 degrees C. or more. The
above-mentioned heating method makes it possible to cool and
solidify the binders, after at least one sort of the binders has
been melted, resulting in enabling the powder for an alloy and/or
the powder for machinability improvement to adhere to the surface
the iron-based powder. Supplementary explaining, under the
above-mentioned minimum temperature, the function for combining,
which the binders have, is not exhibited.
[0059] In case that there are two or more sorts of the binders, it
is more preferable that the heating temperature does not exceed the
maximum value among the melting points of these binders. In case
that the temperature exceeds the above-mentioned maximum
temperature, there is a fear that the adhering function reduces by
thermal-decomposition of the lubricant and so forth. At the same
moment, there is also a fear that the discharge-performance from
hopper deteriorates.
[0060] As a binder, the following ones are exemplified. These are,
at least one, or two or more, selected from the group consisting of
stearic acid, oleamide, stearamide, ethylenebis stearamide, and
melted mixture of stearamide acid ethylenebis stearamide, which are
higher fatty acids or amides thereof.
[0061] Or, this is a heat-melted mixture with the following two
sorts. One is at least one, or two or more, selected from the group
consisting of the oleic acid, spindle oil, and turbine oil. The
other is zinc stearate.
[0062] Besides, a wax is also applicable as a binder in this
invention.
[0063] In this invention, it is preferable that the content of the
binder falls within a range of 0.1 to 1.0 mass part, based on the
amount of the sum total 100 mass part (of iron-based powder, the
powder for an alloy, and machinability improvement particle
powder). Under 0.1 mass part, the segregation-preventing effect for
such as powder for an alloy are not acknowledged. On the other
hand, in case that the content exceeds 1.0 mass parts, the filling
properties of the iron-based mixed powder reduces.
[0064] It goes without saying that the iron-based mixed powder of
this invention is not limited to the one made by above-mentioned
production method.
<Application>
[0065] The iron-based mixed powder of this invention may be
applicable to the manufacturing-method in a general powder
metallurgy. It may be a case, provides manufacturing a various
parts of a machine. Concretely explaining this invention, the
compaction is done by filling up (packing up) with the iron-based
mixed powder to die, and by pressing. In accordance with the
necessity, the corresponding sizing-treatment is done. And the
corresponding sintering is done to bring about a sintered body.
After such a sintering, a heat-treatment is done, these are,
carburizing/quenching (hardening), bright quenching, high frequency
quenching and so forth. And then, a final product such as one of
machine-parts is completed. It goes without saying that some sorts
of working, such as cutting-work, is treated at the respective
appropriate time, resulting in obtaining the final product having a
required and accurate dimension.
EXAMPLES
First Embodiment
Example 1
[0066] The following materials were prepared.
[0067] a) As an iron-based powder 100 kg, the atomized pure iron
powder A (brand: JIP 301A.TM. (product made from JFE Steel Corp.)),
the atomized pure iron powder B (brand: JIP 260A.TM. (product made
from JFE Steel Corp.)) and,
[0068] b) As a powder for an alloy, graphite powder (average
particle diameter: 4 micrometers) or electrolytic cupper powder
(average particle diameter 35 micrometers),
[0069] c) As a powder for a machinability improvement, which has
the kind, the particle diameter and the blending amount shown in
Table 1.
[0070] The above-mentioned-materials a) b) c) were mixed with
lubricant. Afterwards, they were charged into V shaped blender, and
mixed homogeneously to be an iron-based mixed powder. The blending
amount of the powder for an alloy and the powder for a
machinability improvement were determined in mass %, based on the
amount of the sum total of iron-based powder, the powder for an
alloy, and the powder for a machinability improvement.
[0071] The applied lubricant was zinc stearate (average particle
diameter: 20 micrometers), and the lubricant was determined to have
the blending amount (weight part) shown in Table 1, based on the
amount of sum totals 100 weight part of iron-based powder, the
powder for an alloy, and the powder for a machinability
improvement.
[0072] Supplementary explaining, in some of the iron-based mixed
powder, the powder for machinability improvement was not blended
into the mixed materials in order to demonstrate a comparative
example clearly.
[0073] These iron-based mixed powder was filled into the die, and
compacted by pressing, resulting in green compact (ring-shaped
specimen A, B). The ring-shaped specimen A (35 mm of outer
diameter.times.14 mm of inner diameter.times.10 mm in height; the
dimension in conformity with radial crashing test specimen in JIS
2507) was provided for compressive rupture test and for measuring
the change-rate of dimension of outer diameter. The ring-shaped
specimen B (60 mm of outer diameter.times.20 mm of inner
diameter.times.25 mm in height) was provided for the turning test
(cutting while the specimen is turning). The green density was
fixed to 6.6 Mg/m.sup.3. The density was measured by the Archimedes
method. (Note: Archimedes method is defined as a measurement method
by using Archimedes Principle, such that solid existing in liquid
receives buoyancy in terms of weight of the liquid as the same as
the capacity of the solid.)
[0074] Subsequently, the green compact was sintered under the
condition at 1130 degree-C. for 20 min, while using the mesh-belt
type furnace in RX gas (32 vol % H.sub.2-24 vol % CO-0.3 vol %
CO.sub.2-remainder N.sub.2) atmosphere. Resultantly, the sintered
body was obtained. With the obtained sintered body, the compressive
radial crushing test and the turning test were performed.
[0075] The radial crushing test was performed, in accordance with
the regulation of JIS Z 2507, and compressive radial crushing
strength was evaluated.
[0076] The turning test is explained below. At first, three pieces
of the sintered pieces of the ring-shaped specimen B were piled up
to become a cylindrical shape of 75 mm in length. Next, the
outside-surface of the cylindrical shape was cut, using hardmetal
(HTi05T.TM.) byte, while the cylinder was roteted around the axis
of symmetry as the central axis. In order to evaluate a
machinability of the sintered body, a cutting distance was
evaluated. Here, the cutting distance is defined as the distance
that the byte has cut until the flank wear of clearance face (i.e.
wear depth of clearance face) reaches 0.5 mm.
[0077] Operational conditions for turning (cutting the ring
specimen) were determined to be as follow. That is; cutting speed
is 92 m/min, feed per revolution is 0.03 mm/rev, and cutting depth
is 0.89 mm. Typical wearing of a clearance face is shown in FIG. 1.
Also, the physical relationship of the byte and the work material
(sintered body) at the time of cutting is shown in FIG. 2.
[0078] Moreover, during the turning test, the cutting work was once
interrupted at the time when the cutting distance reached 4000 m.
At this time, Rz, which means the surface roughness of machined
surface of the specimen, was measured, based on regulation of JIS B
0601-2001 using the contact type surface roughness gauge.
[0079] The obtained result is shown in Table 1. TABLE-US-00001
TABLE 1 Powder for machinability improvement Content ([--] means no
adding.) Iron- of Powder MnS Calcium phosphate Hydroxy apatite
based Kinds for an alloy Ave. Ave. Ave. Total mixed of Iron- (mass
%)** grain Content grain Content grain Content sum powder based
Graphite Copper size (mass size (mass size (mass (mass No. powder
powder powder (.mu.m) %)** Kinds* (.mu.m) %)** (.mu.m) %) %) 1 A
0.8 2.0 20 0.2 a 5.0 0.6 -- -- 0.8 2 A 0.8 2.0 10 0.1 b 3.6 0.1 5.4
0.1 0.3 3 A 0.8 2.0 4.8 0.1 -- -- -- 1.3 0.4 0.5 4 A 0.8 2.0 3.5
0.1 c 1.7 0.05 -- -- 0.15 5 A 0.8 2.0 4.8 0.2 -- -- -- 3.8 0.1 0.3
6 B 0.9 -- 4.8 0.4 -- -- -- 1.3 0.1 0.5 7 B 0.9 -- 4.8 0.2 b 3.6
0.3 -- -- 0.5 8 B 0.7 -- 4.8 0.3 b 1.7 0.2 -- -- 0.5 9 B 0.7 -- 5.3
0.3 b 3.6 0.2 -- -- 0.5 10 B 0.7 -- 5.1 0.5 -- -- -- -- -- 0.5 11 B
0.7 -- -- -- -- -- -- -- -- -- 12 A 0.8 2.0 10 0.4 -- -- -- -- --
0.4 13 B 0.7 -- -- -- -- -- -- 3.8 0.5 0.5 14 A 0.8 2.0 25 0.2 a
5.0 0.6 -- -- 0.8 Iron- Characteristics of sintered body based
Lubricant Machinability mixed Kinds: Radial Crushing Surface powder
Content strength Cutting distance roughness No. (mass part)*** MPa
(m) Rz (.mu.m) Remarks 1 Zinc 725 29000 9.2 Examples 2 stearate:
728 28000 9.8 Examples 3 0.8 730 30000 9.0 Examples 4 725 27000 8.7
Examples 5 720 25000 8.8 Examples 6 610 30000 9.1 Examples 7 615
28000 8.8 Examples 8 611 24000 8.7 Examples 9 609 26000 8.9
Examples 10 614 10000 9.0 Comparative examples 11 614 4000 15.3
Comparative examples 12 729 6000 9.3 Comparative examples 13 611
5000 9.1 Comparative examples 14 750 12000 14.1 Examples**** Note
1) Within a column of the signed mark * in the above-mentioned
Table 1, `a` means `Tricalcium phosphate`, `b` means `Calcium
hydrogen phosphate, `c` means `Calcium dihydrogen phosphate`. Note
2) Within a column of the signed mark ** in the above-mentioned
Table 1, Content (mass %) means the content amount based on the sum
total of iron-based powder, powder for an alloy and powder for
machinability improvement. Note 3) Within a column of the signed
mark *** in the above-mentioned Table 1, Content amount (mass part)
means that based on the sum total 100 of the mass part. The sum
total is (iron-based powder + powder for an alloy + powder for
machinability improvement). Note 4) The example of the signed mark
**** in the above-mentioned Table 1 is the example that the average
grain size (diameter) is out of the preferable range.
[0080] In the present invention, the respective examples clearly
demonstrate that the sintered body has a high compressive radial
crushing strength, a long cutting distance for indicating a
tool-life, and excellency in machinability. Therefore, each of
these examples of this invention has excellent characteristics as
iron-based mixed powder. Moreover, these examples make it possible
to reduce the surface roughness Rz after cutting, resulting in
reducing the burden of the further finishing-work. On the other
hand, the comparative example, which spins out from the appropriate
range of this invention, has low compressive radial crushing
strength, or degraded machinability.
Example 2
[0081] The following materials were prepared.
[0082] a) As an iron-based powder, the atomized pure iron powderA
(brand: JIP 301A.TM. (product made from JFE Steel Corp.)).
[0083] b) As a powder for an alloy, graphite powder (average
particle diameter: 18 micrometers) or electrolytic cupper powder
(average particle diameter: 35 micrometers).
[0084] c) As a powder for a machinability improvement, which has
the kind, the particle diameter and the blending amount shown in
Table 2.
[0085] d) A binder, whose kind and the blending amount are shown in
Table 2.
[0086] The above-mentioned materials, a)-d) were blended to be
mixed. Afterwards, they were charged into a heating-mixer. Here,
the materials were cooled, after being heated and mixed at 140
degrees C. (This temperature means a point of higher by 15 degrees
C. than the minimum melting point of a binder.) And then, the mixed
materials came to be an iron-based powder, in which the powder for
an alloy and the powder for a machinability improvement adhered on
the surface of the iron-based powder.
[0087] The blending amount of the powder for an alloy and the
powder for a machinability improvement were determined in mass %,
based on the amount of the sum total of iron-based powder, the
powder for an alloy, and the powder for a machinability
improvement. The blending amount of the binder was determined in a
weight part, based on the amount of sum totals 100 weight part of
iron-based powder, the powder for an alloy, and the powder for a
machinability improvement.
[0088] Subsequently, lubricant was blended with the iron-based
powder to which these segregation-preventing treatment had been
performed. Afterwards, the material was charged into V shaped
blender to be mixed homogeneously for obtaining an iron-based mixed
powder. Lubricant was the kind shown in Table 2. And the blending
amount (mass part) of the lubricant was shown in Table 2, based on
the amount of the sum total 100 mass part of the iron-based powder,
the powder for an alloy, and the powder for a machinability
improvement.
[0089] The obtained iron-based mixed powder was filled into the
die. The compaction was carried out, and it came to be the green
compact (ring-shaped specimen A, B) like Example 1. Subsequently,
like Example 1, this green compact was sintered under the
conditions at 1130 degree-C. and for 20 min in RX gas atmosphere,
while using the mesh-belt type furnace. Resultantly, the sintered
body was obtained. About the obtained sintered body, the
compressive rupture test and the turning test were carried out like
Example 1.
[0090] The obtained result is shown in Table 3. TABLE-US-00002
TABLE 2 Powder for machinability improvement Content ([--] means no
adding.) Iron- of Powder MnS Calcium phosphate Hydroxy apatite
based Kinds for an alloy Ave. Ave. Ave. mixed of Iron- (mass %)**
grain Content grain Content grain Content powder based Graphite
Copper size (mass size (mass size (mass No. powder powder powder
(.mu.m) %)** Kinds* (.mu.m) %)** (.mu.m) %) 21 A 0.8 2.0 4.8 0.2 a
5.0 0.2 -- -- 22 A 0.8 2.0 4.8 0.3 c 1.7 0.1 3.5 0.1 23 B 0.9 --
4.8 0.1 b -- -- 1.3 0.4 24 B 0.9 -- 4.8 0.3 b 3.8 0.2 -- -- 25 A
0.8 2.0 4.8 0.5 -- -- -- -- -- 26 B 0.9 -- 4.8 0.5 -- -- -- -- --
Powder for machinability improvement (continued) Segregation- Iron-
Calcium fluoride Binder preventing Lubricant based Ave. Total
Kinds: treatment Kinds: mixed grain sum Blending Heating Blending
powder size Content (mass amount temperature amount No. (.mu.m)
(mass %)** %) (mass %)*** (.degree. C.) (mass %)*** Remarks 21 5.0
0.1 0.5 Zinc stearate: 140 Zinc stearate: Example 0.35 0.4 Oleic
acid: 0.1 22 -- -- 0.5 Zinc stearate: 140 Zinc stearate: Example
0.35 0.4 Oleic acid: 0.1 23 -- -- 0.5 Mono- 140 Zinc stearate:
Example stearamide: 0.2 0.16 Bisstearamide: Bisstearamide: 0.2 0.24
24 -- -- 0.5 Mono- 140 Zinc stearate: Example stearamide: 0.2 0.1
Bisstearamide: Bisstearamide: 0.2 0.3 25 -- -- 0.5 Zinc stearate:
140 Zinc stearate: Comparative 0.35 0.4 example Oleic acid: 0.1 26
-- -- 0.5 Mono- 140 Zinc stearate: Comparative stearamide: 0.2 0.1
example Bisstearamide: Bisstearamide: 0.2 0.3 Note 1) Within a
column of the signed mark * in the above-mentioned Table 2, `a`
means `Tricalcium phosphate`, `b` means `Calcium hydrogen
phosphate, `c` means `Calcium dihydrogen phosphate`. Note 2) Within
a column of the signed mark ** in the above-mentioned Table 2,
Content (mass %) means the content amount based on the sum total of
iron-based powder, powder for an alloy and powder for machinability
improvement. Note 3) Within a column of the signed mark *** in the
above-mentioned Table 2, Content amount (mass part) means that
based on the sum total 100 of the mass part. The sum total is
(iron-based powder + powder for an alloy + powder for machinability
improvement).
[0091] TABLE-US-00003 TABLE 3 Characteristics of sintered body
Radial Machinability Iron-based crushing Cutting Surface mixed
powder strength distance roughness No. (MPa) (m) Rz (.mu.m) Remarks
21 730 28000 9.0 Examples 22 727 27000 8.9 Examples 23 625 25000
9.3 Examples 24 623 28000 9.2 Examples 25 725 6000 13.8 Comparative
examples 26 630 8000 15.2 Comparative examples
[0092] Like Example 1, the whole of these examples of the present
invention has the high compressive rapture strength of a sintered
body. The cutting distance for judging the tool-life (durability)
is long. Such an examples serves as a sintered body excellent in
machinability. Therefore, the iron-based mixed powder has the
characteristic, which is excellent as iron-based mixed powder.
[0093] As explained up to now, the present invention makes it
possible for the sintered body to be improved about machinability.
This improvement is done without degrading the mechanical
properties of the sintered body. Such improvement enables the
productivity of the sintered body, which requires the cutting-work,
to become higher remarkably, resulting in a brilliant industrial
effect to a great extent.
Second Embodiment
[0094] The 2nd embodiment comprises an iron-based mixed powder, by
mixing iron-based powder, the powder for an alloy, the powder for
machinability improvement, and lubricant. The powder for
machinability improvement comprises manganese sulfide powder and/or
calcium fluoride powder, whose average particle diameter is 1 to 60
micrometers, and whose content is 0.1 to 1.5 mass % in total based
on the amount of sum totals of iron-based powder, the powder for an
alloy, and the powder for machinability improvement.
[0095] Moreover, in this embodiment, it is desirable that it is
characterized that the particle size distribution of the powder,
which consists of at least one sort of manganese sulfide powder and
calcium fluoride powder, is substantially the same as the size
distribution of pores of a sintered body, obtained by compacting
the iron-based mixed powder without adding manganese sulfide powder
or calcium fluoride powder and by sintering the formed iron-based
mixed powder.
[0096] Furthermore, in this invention,
[0097] In order to obtain green density of a certain domain (as
described later), following condition is desirable. The average
particle diameter of manganese sulfide is 1 to 10 micrometers, and
the average particle diameter of calcium fluoride is 20 to 60
micrometers. And the content of calcium fluoride is 20 to 80 mass %
based on the amount of sum totals of manganese sulfide and calcium
fluoride. By sintering such green compact, the sintered body whose
machinability is very good can be obtained.
<Powder for Machinability Improvement>
[0098] This embodiment has the feature in average particle diameter
using manganese sulfide powder and/or calcium fluoride powder,
which are 1 to 60 micrometers as powder for machinability
improvement.
[0099] The machinability improvement effect of manganese sulfide
powder and calcium fluoride powder is provided by the chipping
effect as above-mentioned, i.e. making scraps a fine size. However,
since an intermittent impact was given to a tool by pores, which
exists in a sintered body, there was a problem of the oxidization
on the surface of a tool or quality-of-the-material degradation by
generating of fine cracks inside the tool by an intermittence
impact.
[0100] When the particle size distribution of the powder, which
consists of at least one sort of manganese sulfide powder and
calcium fluoride powder, has a similarity or a resemblance to (or
more preferably, is substantially the same as) the size
distribution of pores of a sintered body obtained by compacting and
sintering without adding manganese sulfide powder or calcium
fluoride powder. The particles of manganese sulfide powder and/or
calcium fluoride powder efficiently fill up with pores in the
sintered body, which is created during compaction and sintering,
resulting in decreasing pores. So, the intermittence impact given
to a tool by the collision with the free surface, which form pores
inside a sintered body, and tool can be eased. Consequently, it can
suppress wear on the surface of a tool, or generation of the fine
small sized crack inside a tool, bringing about an extent ion of a
tool life. Especially, in this invention, a great impact can be
reduced by filling up with a coarse pore that is over 30
micrometers.
[0101] To accomplish the relationship between the particle size
distribution of the powder and the pore size distribution of the
sintered body as discussed in the preceding paragraph, for example,
the following procedure is exemplified. The manganese sulfide
powder and/or calcium fluoride powder is classified by mesh using
ordinary sieving method. On the other hand, the sintered body of an
iron-based mixed powder without any additive for the machinability
improvement (such as the manganese sulfide powder or the calcium
fluoride powder) is prepared by compacting and sintering in an
appointed condition (i.e. equivalent to the predetermined condition
for inventive mixed powder). A section of the sintered body
observed by an optical microscope is photographed. This image is
taken in a computer, and a size for an area of the pore section can
be defined as a diameter of the circle having the same area as the
pore. The pore size distribution, which is an original pore size
distribution in the sintered body without any additive for the
machinability improvement, is represented by the existence ratio of
the number of pores in the aforesaid each mesh section to a total
number of pores in the image. Then, the classified powders of
manganese sulfide powder and/or calcium fluoride powder are blended
by approximately the same ratio with the existence ratio (of the
original pore size distribution) for each mesh section.
[0102] Needless to say, it is preferable that the average particle
diameter of manganese sulfide powder and/or calcium fluoride powder
is substantially the same (or substantially equivalent) as the
original pore size distribution. Note, however, it is not necessary
that the particle size distribution of the aforesaid powder and the
pore size distribution of the aforesaid compact be identical.
Rather, a rough similarity (or resemblance) between the particle
size distribution of the aforesaid powder and the pore size
distribution of the aforesaid compact would have a sufficient
effect. In other words, any process that improves similarity
between the two distributions (i.e. bring the two distributions
closer to substantially the same) enhances the machinability
improvement effect. Therefore, in the above example method, the
differences in the existence ratio in the mesh section is
acceptable even for about 20% of the ratio or about 10 point in
percentage. Same is applied for following simpler method.
[0103] Further, for example, the following procedure is conceivable
as a simpler way, in the case that the average particle diameter of
manganese sulfide powder differs from that of calcium fluoride
powder. The aforesaid original pore size distribution is estimated
by the existence ratio of two groups. Here, the two groups are
defined so that each of the two average particle diameters (of the
manganese sulfide powder and the calcium fluoride powder) to be the
representing value of each one of the groups. For example the two
groups are divided by the arithmetic mean value or the logarithm
mean value of the two average particle diameters. Then, the
manganese sulfide powder and the calcium fluoride powder are
blended such that the ratio of them being approximately the same,
or at least getting closer to the existence ratio (of the original
pore size distribution).
[0104] As for the component having the density of 6.0 to 7.0
Mg/m.sup.3, which is the density of general-purpose iron-based
sintered component, it is preferable to meet the following
condition as a more simplified method for improving the aforesaid
similarity. An average particle diameter of manganese sulfide
powder is 1 to 10 micrometers. And that of calcium fluoride powder
is 20 to 60 micrometers. And further, the content of calcium
fluoride is 20 to 80 mass % based on the amount of sum totals of
manganese sulfide powder and calcium fluoride powder. By satisfying
the condition, manganese sulfide particles and calcium fluoride
particles fill up with pores inside the sintered body and it eases
an intermittence impact effectively, while promoting chipping of
the scraps during cutting the component.
[0105] In this embodiment, a laser diffraction-scattering method
using laser measures the particle diameter of the powder. The
average particle diameter was defined by 50%-accumulation
transmission particle diameter (d.sub.50) by mass. Moreover, the
original pore size distribution is evaluated by the following
procedure. Optical-microscope photograph of cross section of
sintered body, which is practically produced without any additives
for machinability improving, is converted into electronic image by
a scanner. Then, the brightness of the image is binarized into a
clear part and a dark part. Then, the dark part is considered to be
the pore, and the area (cross section) thereof is estimated by the
number of pixels. Each pore size is defined as a diameter of the
circle having the same area as the pore, and then, the existence
ration by number for each size is evaluated.
[0106] In order to effectively utilize the chipping effect and the
effect of reducing intermittence impact, it is desirable that the
powder for machinability improvement is in an amount of 0.1 to 1.5
mass % based on the total amounts of the iron-based powder, the
powder for an alloy, and the powder for machinability
improvement.
<Other Ingredients, Production Method, and Application>
[0107] Other suitable ingredients, suitable production method, and
suitable application applied in this invention are entirely the
same with that described in the terms titled <Iron-based powder,
powder for an alloy, and lubricant>, <Production method>,
and <Application> in (First embodiment), and therefore,
incorporated by reference, in the condition that no obvious
contradiction exists.
Example 3
[0108] The following materials were prepared.
[0109] a) As an iron-based powder 100 kg, the atomized pure iron
powder A (brand: JIP 260A.TM. (product made from JFE Steel
Corp.)),
[0110] b) As a powder for an alloy, graphite powder (average
particle diameter of 4 micrometers). The amount of the graphite
powder is 0.7 mass % based on the amount of sum totals of
iron-based powder, the powder for an alloy, and the powder for
machinability improvement,
[0111] c) As a powder for a machinability improvement, manganese
sulfide powder and/or calcium fluoride powder of average particle
diameters and predetermined blending amounts (mass %) which are
shown in Table 4.
[0112] d) As a lubricant, zinc stearate (average particle diameter:
20 micrometers) as a lubricant, are mixed, whose amount is 0.8 mass
% based on the amount of sum totals 100 mass % of iron-based
powder, the powder for an alloy, and the powder for machinability
improvement.
[0113] The above-mentioned-materials a) to d) were mixed and then,
the iron-based mixed powder was produced.
[0114] In addition, iron-based mixed powders as comparative
examples are prepared, in which a calcium phosphate powder or a
hydroxy apatite powder was blended, or, no powders for
machinability improvement were contained.
[0115] These iron-based mixed powder was filled into the die, and
compacted by pressing, resulting in green compact of the dimensions
of
[0116] A: 35 mm of outer diameter.times.14 mm of inner
diameter.times.10 mm in height; the dimension in conformity with
radial crashing test specimen in JIS 2507, and,
[0117] C: 60 mm of outer diameter.times.10 mm in height;
tablet-shaped specimen for drill cutting test. The green density
was fixed to 6.6 Mg/m.sup.2.
[0118] Subsequently, the specimen green compact was sintered under
the condition at 1150 degree-C. and for 20 min, while using the
mesh-belt type furnace in a gas of 5 vol % H.sub.2-remainder
N.sub.2. Resultantly, the sintered body of sintered density of 6.5
to 6.7 Mg/m.sup.3 was obtained. With the obtained sintered body
(specimen), the radial crushing test in accordance with the
regulation of JIS Z 2507 and the cutting test were performed.
[0119] Drill cutting test was done, using a drill of outer
diameter: 3.0 mm hardmetal (HTi05T.TM.). Drill cutting of the plane
of the tablet-shaped sintered body was carried out on condition of
rotational speed: 800 rpm and 0.02 mm/rev. Torque and amplitude of
the vibration of torque were measured at the time of 200th hole
working, as cutting force. Further, the (maximum) outer flank wear
depth of the drill after 200 hole working was measured and
compared. The appearance of wear of a drill circumferential part is
shown in FIG. 3.
[0120] As for torque and its amplitude of the vibration, a work
material was set to a tool dynamometer (a product of Kistler Japan
Co. Ltd.). Here, while drill cutting work is done, the change of
the torque was measured, when the time passed. FIG. 4 shows the
change of the torque on the time-passage. The torque was estimated
based on the average value of the height of rectangular wave. Based
on the amplitude of the vibration on a rectangular wave, the
variation of the torque was estimated.
[0121] The above test result is shown in Table 4. TABLE-US-00004
TABLE 4 Powder formachinability improvement Characteristics of
sintered body (additive amount (mass %))*/ Max. outer Average grain
diameter flank wear Amplitude Calcium Radial depth of Torque of the
Iron-based hydrogen Hydroxy crushing cutting edge (Nm) vibration of
mixed powder MnS/ phosphate/ apatite/ CaF.sub.2/ strength Hardness
(per 200 (200th torque (Nm) (ID) 4.97 .mu.m 3.81 .mu.m 3.57 .mu.m
33.90 .mu.m (MPa) HRB Holes) (m Hole) (200th Hole) Example1 0.5 --
-- 0.2 445 37 0.035 0.07 0.07 Example2 0.35 -- -- 0.35 453 34 0.038
0.07 0.06 Example3 0.2 -- -- 0.5 490 43 0.053 0.06 0.07 Comparative
-- -- -- -- 471 35 0.155 0.24 0.13 example 1 Comparative 0.7 -- --
-- 455 34 0.041 0.11 0.12 example 2 Comparative -- 0.7 -- -- 460 34
0.100 0.20 0.15 example 3 Comparative -- -- 0.7 -- 476 37 0.095
0.12 0.12 example 4 Comparative -- -- -- 0.7 455 31 0.076 0.11 0.10
example 5 Note 1) Within a column of the signed mark * in the
above-mentioned Table 4, Content (mass %) means the content amount
based on the sum total of iron-based powder, powder for alloy and
powder for machinability improvement. [--]means no adding.
[0122] The present invention brings about very little degradation
of the strength of the sintered body. The outer flank wear of the
drill is very few, which means, equal or less than 0.05 mm.
Furthermore, the cutting power (torque) and the amplitude of the
vibration thereof are very small. The amplitude of the vibration of
the cutting force corresponds to the intermittence impact. In the
present invention, pores inside a sintered body are effectively
reduced, resulting in reducing intermittence impact. On the other
hand, the comparative example (or the conventional example), which
falls out of the range of the example of the present invention,
show that the tool wear, the cutting power and the amplitude of the
vibration of the cutting power increase to a great extent,
resulting in a lot of difficulty to be cut.
[0123] As mentioned above, this embodiment, as well as present
invention, makes it possible for the sintered body to be improved
about machinability. This improvement is done without degrading the
mechanical properties of the sintered body. Such improvement
enables the productivity of the sintered body, which requires the
cutting-work, and tool-life, to become higher remarkably, resulting
in a brilliant industrial effect to a great extent.
* * * * *